I'm new to the Neo-Geo ownership scene after picking up a cabinet at auction so my apologies if this issue has been discussed before, but all I could find was people having sound issues or no sound on all slots at once.
The system was playing ok at first...I had some glitches and sound issues on all slots, but fixed the glitching by a good cleaning of everything. The original sound issues were fixed by a fresh cap kit.
One problem that seemed random at first was the sound in slot 2. Sometimes it worked and other times, when it played the first sound of whatever game I put in there, it would shoot out a Z80 error. Now, I get absolutely no sounds in slot 2. The most interesting part is that the system starts up on slot 1 and the sounds and gameplay are perfect, but if I cycle through to slot 2, the sound stops and the game plays great. BUT when I switch to slot 3 and 4 and back to slot 1, the sounds are still dead. They never come back on in any way until I power down the system.
If I leave slot 2 empty, I can cycle through all the other slots and all the games play perfectly with all sounds in tact. It's obvious at this point that slot 2 is the issue, but I'm not too versed in the schematics of this board to know where to look.
Here's what I've done:
The last bit of info I'll point out because I think it might be important is that there is one LS245 chip on the board that someone before me has modded to include a connection between the ground pin (pin 10) to a closeby ground trace. If I remove this link, the sounds are garbled and messed up. It appears that this chip for some reason does not ground properly in its socket. From what I can tell, there are no other mods on this board.
Ultimately, what I'd like to know is what set of chips are used to control each slot? I know schematics for these boards are non-existent so I'm wondering if anyone knows that path from each slot to the sound area of the board. I'm led to believe that these slots act somewhat independently from each other given that I have sound in 3 of the 4 slots. Any help would be greatly appreciated!!! I can send pics if anyone wants to see something specific.
The system was playing ok at first...I had some glitches and sound issues on all slots, but fixed the glitching by a good cleaning of everything. The original sound issues were fixed by a fresh cap kit.
One problem that seemed random at first was the sound in slot 2. Sometimes it worked and other times, when it played the first sound of whatever game I put in there, it would shoot out a Z80 error. Now, I get absolutely no sounds in slot 2. The most interesting part is that the system starts up on slot 1 and the sounds and gameplay are perfect, but if I cycle through to slot 2, the sound stops and the game plays great. BUT when I switch to slot 3 and 4 and back to slot 1, the sounds are still dead. They never come back on in any way until I power down the system.
If I leave slot 2 empty, I can cycle through all the other slots and all the games play perfectly with all sounds in tact. It's obvious at this point that slot 2 is the issue, but I'm not too versed in the schematics of this board to know where to look.
Here's what I've done:
- Complete cap kit (fixed low volume and some static issues)
- Checked for obvious bad traces
- Checked continuity on the pins inside slot 2 and matched the results with other working slots (it seems slots 1 and 2 are paired as are slots 3 and 4)
- Cleaned all slots and game cartridges using 91% isopropyl alcohol and again with a pencil eraser
- Cleared backup ram
The last bit of info I'll point out because I think it might be important is that there is one LS245 chip on the board that someone before me has modded to include a connection between the ground pin (pin 10) to a closeby ground trace. If I remove this link, the sounds are garbled and messed up. It appears that this chip for some reason does not ground properly in its socket. From what I can tell, there are no other mods on this board.
Ultimately, what I'd like to know is what set of chips are used to control each slot? I know schematics for these boards are non-existent so I'm wondering if anyone knows that path from each slot to the sound area of the board. I'm led to believe that these slots act somewhat independently from each other given that I have sound in 3 of the 4 slots. Any help would be greatly appreciated!!! I can send pics if anyone wants to see something specific.
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